Dominant Firms' Wealth Attracts
Investors -- and Antitrust Probes

Microsoft Corp., Intel Corp. and Coca-Cola Co. have been among the biggest creators of shareholder wealth during the 1990s bull market. They have also all come in for antitrust scrutiny.

It may not be a coincidence.

These blue-chip growth companies boast enormous market shares, strong franchises and brand names and often the ability to expand profit margins in a highly competitive economy. These qualities are key to delivering...